Pipe joints have in the past been made between pipes in which a bell or socket formed at one end of each pipe section and the opposite end of the adjacent pipe section is inserted in the bell or socket. In order to produce a tight joint, packings of soft metal, asphaltic material or like substances, have been introduced before the pipe sections are forced together. Alternatively, the pipe sections are welded at the joint and thus a tight joint is secured. Another example is found in the joints in tube sections of vacuum cleaners. Here a bell with an internal diameter only slightly larger than the outside diameter of the section to which it is joined is utilized so that a close fitting joint results and the slight friction between the parts is sufficient to make the joint free from accidental separation of the pipe sections. In all such applications carefully controlled tolerances between the mating diameters are maintained.
U.S. Pat. No. 3,466,738 issued to Wadsworth W. Mount on Sept. 16, 1969 discloses a method for joining pipe sections having comparatively thin walls relative to the diameter, which pipe sections may be of exactly equal nominal size and wall thickness and may be forced into overlapping engagement without subjecting either of the pipe sections at the joint to stresses in excess of the rupture limit of the steel of which the pipes are formed. The elasticity of the outer pipe at the joint makes an extremely tight joint without reliance on predetermined tolerances and may require many thousands of pounds of force to press the sections together and thereafter to pull apart. Furthermore, the complete joint retains nearly the same original inside diameter on the inside pipe when two pipes are joined by this method.
It is an object of the present invention to provide a press-fitted pipe joint with significantly improved joint strength relative to the pipe joints which are formed according to the method of the above patent. The object of this invention is achieved by forming the outer or bell end of one of the pipe sections so that it has a greater wall thickness than the inner or pin end of the other pipe section.